Mega Gravity Gun

You are able to get the Mega Gravity GunHalf-Life 2 and Half-Life 2: Episode One while in the Citadel. You walk through a security room that is suppose to destroy all of your weapons. When it starts to destroy the Gravity Gun, it actually super charges it, making it the Mega Gravity Gun. With your new weapon, you can punt NPC's, pick up dead bodies, and pick up heavier objects.

But, all good things must come to an end. When you leave the Citadel, the Mega Gravity Gun looses its charge and becomes the Gravity Gun.